The present invention relates to a front vehicle-body structure of a vehicle which comprises a front side frame having a closed cross section extending in a vehicle longitudinal direction and including a mount-bracket attachment part for attaching a mount bracket provided at a powertrain mount for supporting a powertrain and a crash can attached to a front end of the front side frame.
It is known that a gusset member as a reinforcing member is provided at a front side frame as exemplified in Japanese Patent Laid-Open Publication No. 2013-193571 and US Patent Application Publication No. 2013/0140852 A1. The above-described first patent document discloses a structure which comprises a front side frame (1), a lower member (3) which is arranged on an outward side, in a vehicle width direction, of this front side frame, and a gusset (2) which extends in a vehicle longitudinal direction from a front end of the front side frame (1) to a first breaking point (P1) between the front side frame (1) and the lower member (3), whereby a collision load can be securely transmitted to the front side frame (1) via the lower member (3) and the gusset (2) in a vehicle offset collision.
Further, a bulkhead (13) as the gusset member for receiving and supporting the collision load transmitted from the gusset (2) in the vehicle offset collision is provided inside the front side frame (1).
The above-described second patent document discloses a structure in which a front side frame (11) is provided with connection portions (18) (19) for supporting engine mounts (30) at front-and-rear points so as to reduce engine vibrations transmitted to a cabin side via the engine mounts (30), and at these connection portions (18) (19) are provided partitioning walls (82) (92) as a gusset member so as to improve support strength of the engine mounts (30).
Herein, it is known that a crash can is compressively deformed or a front side frame is broken and deformed at a specified breaking point in a vehicle frontal collision.
The present inventors have found that since a front-side portion of the front side frame can be made to perform the load absorption function aggressively by compressively deforming this front side portion, thereby effectively improving the load absorption performance of the front side frame in the vehicle frontal collision.
However, in a case where the front-side portion of the front side frame is configured to have low strength in order to compressively deform this portion in the vehicle frontal collision, the front-side portion of the front side frame tends to be easily deformed such that its cross section perpendicular to the vehicle longitudinal direction is crushed when a gear noise (engine noise) transmitted from the powertrain to a vehicle-body side via the powertrain mount (engine mount) is transmitted to this front-side portion. Consequently, there is a concern that the vibration is so amplified and transmitted to the cabin side that a vehicle passenger may have uncomfortable feelings, thereby deteriorating the NVH performance improperly.
The front side frame of the above-described first patent document is configured such that plural breaking points (P1-P3) are formed so as to break and deform this frame when receiving the frontal-collision load in the vehicle longitudinal direction and a bulkhead (13) is arranged inside this frame so as not to block this frame's breaking at the above-described breaking points. Further, the front-side portion of the front side frame is configured to have high strength by providing the gusset (2) at an outward-side face of this front-side portion along the vehicle longitudinal direction as described above.
However, the above-described first patent document has no description about a deformation mode based on the above-described concept that the front-side portion of the front side frame is made to perform the impact-load absorption function aggressively by compressively deforming the front side portion or about a structure in which the compressive deformation of the front-side portion of the front side frame in the vehicle frontal collision is not blocked by configuring this front-side portion to have the low strength. Thus, there is room for improvement of the load absorption performance of the front side frame.
Meanwhile, the above-described second patent document discloses the structure in which the partitioning walls (82) (92) are provided at the support position of the engine mounts (30), but not disclose any structure for increasing the strength of the front-side portion of the front side frame which is positioned in front of the engine mounts (30) by providing a partitioning wall at this front-side portion, for example. Thus, there is room for investigation of the above-described concern that the gear noise is transmitted to the low-strength front-side portion of the front side frame via the engine mount and thereby so amplified that the NVH performance may be deteriorated.
That is, while both of the front side frames disclosed in the above-described patent documents comprise the gusset member as the reinforcing member, the load absorption performance in the vehicle frontal collision and the NVH performance cannot be compatibly achieved properly by these disclosed front side frames.